Impact of nonequilibrium phonons on the electron dynamics in terahertz quantum cascade lasers

In this paper we investigate, both theoretically and experimentally, nonequilibrium electron and phonon effects in quantum-cascade devices. In particular, we have developed a Monte Carlo-based global kinetic approach describing the complete interacting electronic subsystem (i.e., the full set of active-region and injector subbands) coupled to out-of-equilibrium longitudinal polar-optical (LO) phonons, which in turn will decay anharmonically into thermalized acoustic modes. Simulated results obtained for a prototypical terahertz emitting device show a very good agreement with measured data, evidencing how the nonequilibrium LO phonon population affects the electro-optical device performances. The latter may be qualitatively reproduced in terms of a global effective temperature of the heated phononic system.